Communication system



June 3, 1930. F, CARTER 1,761 {776 COMMUNICATION SYSTEM Filed Aug. 15, 1927 Inventori Emmett-,1. Carter by I His Attorney mmnrr r. camnn, or scnmrncrnnr,

Patented June 3, 193i)- Pa r gzur OFFICE NEW YORK, AssIGNonro GENERAL nnxc'rmc CbMPANY, A CORPORATION OF NEW YORK commumcarron SYSTEM Application filed August 15, 1927. Serial No. 212,880.

My invention relates to carrier currentcommunication systems and more particularly to extension apparatus for use in connecf the usual power distribution system, it is.

tion therewith.

In connection with the operation of carrier current communication systems, such as are employed for communication over the lines deslrable to extend the service of the carrier system to parties remote from the carrier station.

One of the objects of my present invention is to provide an extension system whereby a party located at a point remote from the carrier station may control the carrier station to selectively call remote stations through the carrier channel and communicate therewith,

- and whereby the extension station may, simi- Y larly, be called from the remote stations through the carrier channel.

A further object of the invention is to provide such an extension system in which both calling and signaling is eflected over a single pair 'of line conductors extending between the carrier station and extension station.

" rier station over lines which are mounted on the supports which are provided for the conductors of such power distribution systems.

These vlines usually 'have considerable voltage impressed thereon from the ower conductors and are, therefore, unfit or low frequency signaling or control except as means are provided for overcoming the noise, and

singing, resulting from this interference.

Accordingly, a further object of my invention is to provide means whereby such con-- ductors may be economically employed for communication between the said party and the carrier station. Another purpose of my invention is to. provide means whereby an operator at a remote station, such as that indicated, may utilize such power conductors to control the carrier station in a manner similar to that in which the operator at the carrier station itself may control it and with siractically the same efliciency and facility. till a further purpose of my invention is to provide means which are economical in construction and reliable in its operation whereby the service of the carrier system may be made available to the remote operator, notwithstanding that the intervening line is subject to severe interference of the type mentioned.

v The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims.

My invention itself, however, both as to itsorganization and method of operation, to-

gether with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which the single figure represents an embodiment of my invention.

Referring to the drawing, B represents a carrier current signal station which is provided with the usual transmitting system 1 and receiving system 2 having associated therewith the usual telephone instrument 3, 4, by means of which an operator is enabled to communicate by means of carrier currents transmitted over a power distribution system 5 or other carrier current channel with remote points located upon said channel. A represents an operators station which is located at a point remote from the station B, but which maybe interconnected therewith by means of a'pair of conductors 6 which are mounted upon supports which are primarily provided for power distribution conductors. Due to interference from the power distribution system these conductors have impressed thereon considerable voltage and are,

therefore, unfit for the usual audio frequency or direct current communication or relaycontrol. In accordance with my invention I provide means whereby signaling and con- "trol may be had over these conductors by means of carrier current in one direction and by means of audio frequency currents 1n the 'other'direction. By providing that the audio frequency currents have a sultable intensity ratio with respect to the noise currents on the conductors 6, it will be seen that the effect of these noise currents upon the communication-between the points A and B will be eliminated. It will also be seen that this is effected \vithout' encountering the diflicult balancing andsinging-problems which are involved in connection with the use of two way audio repeating systems when utilized in connection witl1 currents of this kind and furthermore, the simple expedient of c iokc coils may be employed to separate the signals being transmitted in opposite directions at the diltcrent stations.

Accordingly, I provide at the station A a carrier current oscillation generator 7 and modulating device 8 therefor for supplying to the line 6 carrier current modulated with signaling current, the latter of which may be impressed upon the grid of the device 8 from the transmitter 9 of the operators telephone.

These currents may be transmitted through an output transformer 10.coupling condensers 11 and switching means 12 to the conductors 6. At the station B these currents will be received in a suitable tuned circuit 13 and impressed upon the detector 14, where they -will be demodulated and the signaling currents supplied therefrom through a suitable audio amplifier 15 to the audio channel 16of the transmitter 1'. Connected in parallel with the audio channel 16 of the transmitter 1 is the secondary winding of a transformer 17, the primary winding of which is connected in parallel with thetransmitter 4 of the telephone of the operator at the station B. The audio channel 18 of the receiver 2 at the station B is connected through a contact 19 and armature of the relay 20, the purpose of which will be later set forth, to the primary winding of an insulation transformer 21, the secondary winding of which is connected through suitable radio frequency choke coils 22 and switching means'23 to the extension conductor 6. The receiver'of the telephone at the station A is connected through a pair of contacts 24 which are associated with the receiver hook to the secondary winding of an insulation transformer 25, the primary winding of which is connected throu h radio frequency choke coils 26 and switching device 12 to the extension conductor 6. The choke coils 22 and 26 offer high impedance to-currents of carrier frequency and low impedance to currents of audio frequency. It will thus be seen that, with the apparatus as thus far described in its operative condition, the operator at the station A by speakin into his transmitter 9 may impress audio frequency currents upon the ltransmitting system 1 in the same manner as may be done by the operator at the station B. Likewise it will be seen that the operator at the station A, by listening at thexreceiver 27, may hear the signals received from the distribution system 5 by the 'du'ctors 31;

ed between the station Band the station A,

and means whereby the station B may be controlled by the operator at the station A over the line 6 in the same manner as may be done by the operator at the station B. Describing: more particularly the apparatus at the station A, 28 represents a transformer the primary winding of which is connected through the contacts of a relay 29 to a source of alternating current potential 30. A secondary winding of this transformer is adapted to energize the cathodes of the modulating device 8 and oscillator 7 through a circuit including con- 32 represents an electron discharge device, the cathode of which is energized from a winding 33- on the transformer 28. This device is utilized for the purpose of rectifying the alternating currentfrom the source 30 and supplying a direct current potcntial to the anodes of the oscillation generator 7 and the n'iodulator 8. Forthis purpose it is connected in a circuit extending through the winding 34 of the transformer 30, conductor 35, resistance 36, contacts of a relay 37 conductors 31, space between the cathode and anode of the oscillation generator 7 primary winding of thd transformer 10,- radio frequency choke coil 38, conductor 39, snuhithing reactor 40 to the cathode of the device 32. Since the anode and cathode of the device-8 are connected between the conductors 31 and the radio frequency choke coil 38 both of the devices 7 and 8 will be supplied with direct current potential from the device 32. The actuating coil of the relay 29 is adapted to be energized from a source of potential 41 through a pair of contacts 42 which are operated in accordance with the position of the receiver hook. Thus when the operator res movesthe receiver 27 from the hook the contacts 42 are moved to their closed position and from the anode of the discharge device 32 the relay is energized to close its contacts, and

. thereby to energize the circuits of the devices 7 and 8. The actuating coil of the relay 37, the contacts of which are connected in the anode circuit of these devices, is likewise adapted to be energized from the source of potential 41 through a circuit including the conductor 43, source of potential 41, contacts '42 and dialing contacts 44,' Thus the opera- 15 is energized from a source of potential 48 through the primary winding of a transformer 49; and the anode circuit of the detector 14 is energized from the source of potential 48, through a circuit extending from the positive side of the source of potential through conductor 49, actuating coil of a relay 50 tothe anode of the detector 14, space between the anode and cathode of this detector and thence back to the negative side of the source of potential 48. Thus when carrier currents interrupted in accordance with the operation of the contacts 44 are impressed upon the detector 14 the relay 50 is thereby actuatinga relay 54 which is connected in a circuit extending from the negative side of the source of potential 46 through the lower contacts of the relay 51, actuating coil of the relay 54 to the positive side of the source of potential 46. The relay 54 may constitute the dialing relay of the transmitter 1 and is adapted by means of its lower contact to close the keying circuit 55 of the transmitter 1, thereby causing the 'transmitter to transmit carrier to the system 5 having interruptions therein in accordance with those received from the station A. The upper contacts of the relay 54 are connected in a circuit leading from the negative sideof the source of potential 46 through these contacts to a pair of selecting devices 56 and 57' to the positive side of the source of potential. These selecting devices are adapted to close their contacts only in response to current impulses received in a particular code combination. Thus, for example, if the operator at the station A dials the number'of the station B, the selector 56 will respond, thereby closing its contacts to actuate the signaling device 58 of the station B. The relay 52, which is adapted to be.

energized in response to the closing of the upper contacts, of the relay 51 from the source of potential 48, is somewhat sluggish in opening its contacts and therefore will not I follow the. dialing interruptions. The relay 20 1s operated in response to the closing of the contacts of relay 52, and thereby closes an energizing circuit of the transmitter 1 includmg conductors 59. Likewise, by means of the contact 19, this relay is adapted to connect the primary windingof the insulation transformer 21 directly to the audio frequency channel of the receiver 2.

Thus the operator at the station A by dialing the proper code numberimay actuateithe signaling device 58 of'the s'tatlon B, or he may actuate the keying contacts of the relay 54in a manner to key the output from transmitter 1 in accordance with the code number of any station upon the distribution system 5. Means are likewise provided whereby any station upon the distribution system 5 may operate the signaling device of the statioIi B, or that of the station A. To this end .a relay 60 having contacts which are connectcd in parallel with the contacts of relay 54 is adapted to respond to carrier impulses received from the distribution system 5. Thus if these impulses correspond to the code number of the station 13 the selector 56 will be caused to respond to actuate the signaling device 58, Whereas if the received impulses correspond to the code number of the station A the selector 57 will respond to close its I contacts. Relay 61 is adapted to be energized from the source oipotential 46 through the contacts of the relay 57 and when it is so energized it will close a circuit leading from the negative side of the seurce of potential 46 t'hroughthe direct current side of a rotary converter 62, contacts of the relay 61, conductor 63, source of potential 48, right-hand conductor 47 and source of potential 46.

This rotary converter, which is normally inoperative, will then be started and caused to supnlv alternating current through a circuit including conductor 64, alternating current side of the converter61, conductor 65,

lower contact and armature of the relay 20 1 and conductor 66'to the primary winding of the insulation transformer 21. Thus upon closing of the contacts of the relay 57 alternating current will be supplied through the transformer 21, extension circuit 6 and transformer 25 to the signaling device 67 of the station A.

The dialing contacts 68 of the telephone at the station B are connected in parallel with the lower contacts of the relay 51 and consequently they are effective to operate the dialing relay 54 and to key the transmitter in accordance with any desired code number. If the operator operates these contacts in accordance with the code number of station A, the selector 57 will respond to energize the rotary converter 62 in the same manner in which it does in response to the operation of the relay 60.

' It will be seen that theoperator at either the station A or the station B may operate the signaling device-of the other station or that of any station upon the distribution system I 5. Thus, for example, if the operator at the station B desires to talk with the operator at the station A, he. removes his receiver 3 from sion circuit6 to the signaling device 68. The operatorat the station A then removes his receiver from the hook,.thereby energizing his transmitting circuit and causing it to supply carrier currents from the extension circuit (3 to the detector 14. When the operator at, the station A speaks into.the transmitter 9 these voice currents will be detected by the detector 14, amplified by the audio frequency amplifier and supplied to the transmitter 1. A portion of the output current'of the waycommunication may be had between the station A, B and the particular' station upon the distribution system 5.

To prevent the noise resulting from the 1n- -terference in the conductors 6 from interfer- .ing with the reception of signals from the station B at the station A, the receiver 2 is adapted to supply an audio output which has a desired intensity ratio to the noise currents "of the conductor 6. In order that these cur-' rents will not be too great for thereceiver 3 a resistance 69 1s 1nserted in series therewith, and likewise a resistance 70 is inserted in circuit with the receiver 27 at the station A. It will be seen that this latter resistance will not only'attenuate the signaling current but will also attenuate noise currents, thereby substantially eliminating the eflect of the latter.

While I have shown and described a particular embodiment of my invention, it will, of course, be understood that I do not wish to be limited thereto since many modifications, both in the circuit arrangement and in the instrumentalities employed, maybe made without departing from the spirit and scope of my invention as set forth in the appended claims. What I'claim as new and desire-to secure by Letters Patent of the United States, is

1. In a signaling'system, a line, signaling stations at" different points on said line, said line being subject to noise currentsof magnitude sufiicient to prevent satisfactory twoway audio communication between'said stations, means for impressing acarrier wave modulated by signaling currents upon said line at one of said stations, means at another of said stations for detectingsaid; signaling currents from said carrier wave, means at said other stationfor impressing signaling currents directly upon said line having a desired intensity ratio with respect to noise currents appearing in sald hne, and means at said first station for attenuating said noise 7 currents sufliciently to permit desired recepa tion of the signal currents.

2. In a signaling system, a line, a carrier rier channel and means at said second station,

adapted to detect signaling currents received fromsaid carrier channel and to supply said signaling currents directly to said line.

3. In a signaling system, a line, a carrier channel in addition to said line, a signaling station adapted to, supply a carrier wave modulatedwith signaling currents to said line, a second station adapted to receive said signaling currents from said line and to repeat said. signaling currents to said carrier channel, and means at said second station adapted to detect signaling currents received from said carrier channel and to supply said signaling currents directly to said line with a desired intensity relation to noise currents in said line, and means at said firststation for attenuating said noise and signal currents.

4. In combinatioma carrier channel, a carrier station having a transmitter and receiver adapted for two way communication over said channel, a second station, aline connectting said stations, said second station being adapted to supply a carrier wave modulated with audio frequency currents to said line and to receive audio frequency currentsdirectly from said line, detecting means connecting said line with the audio frequency channels of said transmitter, and means connecting said line with the audio frequency channels of said receiver. 1

5. In combination, a carrier channel, a carrier station having a transmitter and receiver adapted for two way communication oversaid channel, a second station, a ,line connecting said stations, said second statiombeing adaptedto supply a carrier wave modulated with audio frequency currents to said line and to receive audio frequency currents directly from said line, detecting means connecting said line with the audio frequency channels of said transmitter and means responsive to received carrier for energizing said transmitter and connecting said line with the audio frequency channels of said receiver. v i

6. In combination, a carrierchannel, a carrier station having a transmitter and receiver adapted for two way communication- 'over said channel, a second station, a line connect ing said-stations, said second station being adapted to supply a carrier'wave modulatedwith audio frequency currents to said line necting said line with the audio frequency channels of said transmitter, keying for producing interruptions in the output from each of said stations, the keying means for saidfirst station being operable responsively to interruptions in the carrier received from said second station, and means responsive tocarrier received from said first station for connecting said line to the audio frequency channels of said receiver. I In combination, a carrier channel,a carrier station having a transmitter and receiver adapted for two way communication over said channel, a second station, a line connecting said stations,'said second stat-ion being adapted to supply a carrier wave modulated with audio frequency currents to said line and to receive audio frequency currents directly from said, line, detecting means con- 0 necting said line with the audio frequency "channels of said transmitter and means connecting said line with the audio frequency channels of said receiver, a control circuit for said --first station, and means responsive to carrier received from said second station for energizing said control circuit. 8. A transmission system comprising a power line adapted for the simultaneous transmission of power currents and signal waves, signal stations connected -to said power line, means for one station to selectively call another station and to efiect communication therewith,an extension station, conductors for connecting the extension station.

to one of said power line stations to permit calling and signaling over the same conductors,'and means operated at said extension station through the associated si nal station for selectively calling the power fine stations 40 and for communicating therewith.

- 9. In a transmission system, a power line for transmitting high tension power currents, signal stations connected to said power line, means at said signal stations for calling and signaling over saidpower line'by carrier current waves, an extenslon station,

conductors for connectinosaid extension sta tion to one of said signal stations to permit calling and signaling over the same conductors, and'means operated at said extension station through the associated signal station for selectively calling and signaling said signal stations connected to the power line.

10. In a transmission system, a power line for transmitting high tension power currents and carrier'wave signal currents, signal sta-' tions connected to said power line, means comprising carrier current transmitting and receiving apparatus-at each of said signal stations for selectively calling and for eflecting communication between stations, an extension station, conductors for connecting said extension station to one of said signal stations to permit calling and signalling over the same conductors andwmeans at said extension station for calling'and communicatmeans ing with the associated signal station and for controlling the. carrier current transmit ting and receiving apparatus at the'associated signal station to selectively call and signal the various signal stations.

11. vIn a power line carrier telephone system,"a power line, signal stations connected to said line and having carrier current apparatus for calling other stations and for affecting telephone communication therewith,

an extension station, conductors for connect- A ing the extension station to one of said signal stations to permit calling and signaling over the same conductors, means controlled by signal stations connected to the power line foroperating the carriercur'rent apparatus at the signal stations associated with the ex tension station to selectively call either the extension station or the signal station associated therewith, and means operative upon carrier current apparatus at the associated signal station for telephone communication between the extension station and signal stations. Y

12. A communication system comprising a power liile adapted for simultaneous transmission'of power currents and signal waves, carrier current signal stations connected to said power lines, means in each of said stations for selectively calling another station and to effect communication therewith, an extension station, line conductors extending between said extension station and one of said signal stations, and means for selectively calling any of said signal stations from said extension station and to call said extension station from any of said signal stations and to effect communication between the calling and called stations over said line conductors.

power line adapted for the simultaneous 13. A transmission system comprising a v.removal of the receiver at the extension station from the switch hook for preparin the transmission of power currents and signal waves, signal stations connected to said powerv lines, means for one station to selectively call another station and to efiect communication therewith, an extension station, a single pair of line conductors extendlng between the extension station and one of sand signal stations, and means at the extension station'and associated signal station to effect both calling and signaling in both directions between said extension station and any of said signal stations over said single pair of line conductors. j

14. In a transmission system, a power hne for transmitting high tension power currents and carrier wave signal currents, signal stations connected to said power line, an extension station, conductors for connecting sald extension station to one of said signal stations to permit'calling and signaling over the same conductors, carrier current transmitting and receiving apparatus at each of said signal stations, means at each signal station for controlling said carrier current appara- 5 tus to selectively si nal and effect tele hone communication wit any other signa station, means at said extension station for operating the carrier current apparatus at the associated signal station to selectively call and to effect telephone communication with the other signal stations, and means for effecting telephone communication between the extension station and the associated signal station, said'means utilizing the carrier current transmitting and receiving appara-- tus at the associated signal station to transmit telephone currents from said associated signal station to the extension station.

In witness whereof, I have hereunto set my hand this 11th day of August 1927.

EMMETT F. CARTER. 

